A typical compressor comprises a crank case having a rotatable crank shaft driven by a prime mover such as a motor. The crank shaft drives a piston in a piston chamber through a connecting rod. The piston is provided with the usual seal to provide a gas and liquid tight seal between the piston and the inner cylinder walls. The outer end of the piston cylinder mounts a cylinder head having inlet and outlet ports which typically transfer gas and/or liquid or combinations of the two from the inlet port through the piston chamber and out the outlet port. For example, the inlet port may be connected by a flexible line to a unit containing a gas/liquid refrigerant and the outlet port is connected through a flexible line to a portable refrigerant storage container or the compressor may be used as one element of a more complicated refrigerant recovery and/or recharging unit. These systems would typically be used to safely drain and/or recharge air conditioning units or other refrigerating devices or apparatus using Chlorinated Fluorocarbons (CFC's), Hydro Chloro Fluorocarbons (HCFC's), Hydro Fluorocarbons (HFC's) or other refrigerants. Typically the cylinder head has an arrangement of valves for controlling flow of refrigerant from the inlet and outlet ports to and from the piston cylinder. Typically these valves are either of the poppet type or reed valves.
It has been found that these systems while generally effective for the purposes intended have certain disadvantages and drawbacks. For example, reeds of a typical reed valve are rather delicate and the spring action of these valves over a period of time may result in fatigue failures. Also due to their delicate nature, the reed valves may not tolerate liquid flow or mixed liquid and gas flow without breaking. When the reeds fail they disrupt normal operation of the compressor and may be ingested into the cylinder. It has been found that in some instances spring biased poppet valves are drawn directly into the piston chamber causing compressor failure and sometimes permanent damage such as scoring of the piston walls or distortion of other parts due to jamming. Another failure mode involves failure of the spring or of the spring keeper details causing loss of compressor function and damage to parts. Repair or replacement of failed or damaged parts is time consuming and expensive. Furthermore in these known designs utilizing springs, the spring forces must be overcome by gas pressure differentials and this reduces the compressor volumetric efficiency and also limits pressure ratio capabilities. Additionally, the springs must be carefully controlled as to their manufactured stiffness, dimensions and other properties as well as their installation.
Pumping systems for pumping gases and fluids are not new per se. Prior art patents of interest include the following: